1. Technical Field
The present invention relates generally to cellular wireless networks; and more particularly to the servicing of packetized communications within such cellular wireless networks.
2. Related Art
Wireless networks are well known. Cellular wireless networks support wireless communication services in many populated areas of the world. While wireless networks were initially constructed to service voice circuit-switched voice communications, they are now called upon to support packet-switched data communications as well.
The transmission of packetized data communications within a wireless network places different demands on networks than does the transmission of voice communications. Voice communications require a sustained bandwidth with minimum signal-to-noise ratio (SNR) and continuity requirements. Data communications, on the other hand, typically are latency tolerant but have higher total throughput requirements. Conventional circuit-switched wireless networks were designed to support the well-known voice communication requirements. Thus, wireless networks (as well as conventional circuit switched telephone networks) have been adapted to service data communications, with such adaptation providing mixed results. Thus, future wired and wireless networks will likely be fully packet switched.
The Internet, Intranets, Wide Area Networks, and Local Area Networks are all packet switched networks. In such packet switched networks, all communications to be transmitted from a source to a destination are packetized prior to transmission and reassembled upon receipt. These networks are capable of servicing both data communications and Voice Over Internet Protocol (VOIP) communications. Because of the requirement of interoperability between the equipment of differing vendors, various interworking standards have been developed for packet switched networks. Many operating standards of this type are based upon hierarchical protocol systems, e.g., the Industry Standards Organization (ISO) seven layer Open Systems Interconnect (OSI) model, the TCP/IP model, etc. The OSI model includes, from lowest protocol layer to highest protocol layer, (1) the physical layer, (2) the data link layer, (3) the network layer, (4) the transport layer, (5) the session layer, (6) the presentation layer, and (7) the application layer. A corresponding TCP/IP reference model includes (1) the physical layer, (2) the network interface layer, (3) the Internet layer, (4) the transport layer, and (5) the application layer. Networked devices, e.g. computer terminals, wireless network mobile stations, etc., operating according to these standards support error free transfer of data communications. Thus, almost all devices supporting data communications operate according to one or more variations of these operating standards.
In order to ensure that packets lost in transmission are retransmitted, the operating standards sometimes employ Automatic Retransmission reQuest (ARQ) operations. Generally speaking, ARQ operations are employed to automatically request retransmission of data packets that have been transmitted but not successfully received, e.g., lost data packets, erroneous data packets, etc.
For example, in a data session established between a client computer and a web server across the Internet, the client computer requests the download of a file. The web server accesses the file, subdivides the requested file into a plurality of data packets, and uniquely identifies each data packet. The web server then transmits each of the data packets to the client computer. Upon receipt of all of the data packets, the client computer combines the data packets in the correct order to reconstruct the file. However, the client computer may not successfully receive all of the data packets from the web computer due to lost/erroneous transmissions. When this occurs, the client computer automatically sends a request to the web server to retransmit a lost/erroneously-received packet. ARQ operations continue until the client computer correctly receives all data packets that make up the file.
ARQ operations are particularly important in wireless networks, e.g., cellular networks that include wireless links between a base station and a serviced mobile station. Wireless links are subject to interference, fading, and other factors that oftentimes prevent the successful transmission of data packets. Thus, in such systems, ARQ operations are particularly important and are implemented between the serviced mobile station and the servicing base station. These ARQ operations are different than the ARQ operations described above since the base station does not serve as an end point to the serviced communication. However, existing ARQ schemes require significant overhead and heretofore have not provided required robustness without incurring significant additional overhead and without oftentimes resulting in unneeded retransmissions.
Thus, there exists a need in the art for ARQ operations in wireless networks that will provide robust operations across the wireless link and that will also consume little additional overhead.